The concept of Pythagorean fuzzy sets was introduced by Yager in 2013. It is a generalization of the concepts of fuzzy sets and intuitionistic fuzzy sets. The aim of this study was to apply the concept of Pythagorean fuzzy sets to clarify in KUalgebras. The notion of Pythagorean fuzzy KU-subalgebras of KU-algebras is introduced. Then, we give some fundamental properties of Pythagorean fuzzy KU-subalgebras in KU-algebras. Finally, we investigate the relationships between the image and the preimage of Pythagorean fuzzy KU-subalgebras under a homomorphism of KU-algebras.